A few years ago there was a very painful attempt at porting from
libsoup2 to libsoup3. Flatpak libsoup3 support never landed and it seems
like a large amount of distros have switched over to libcurl instead.
This commit removes libsoup2 support completely instead of growing
libsoup3 support.
Closes#5915Closes#4582
Autotools support was removed as of commit 8e63eda,
remove mention of the Autotools support in the CONTRIBUTING file
Signed-off-by: Ryan Brue <ryanbrue.dev@gmail.com>